Wireless communication device, wireless communication system, controlling method for wireless communication device, and recording medium storing program

ABSTRACT

To improve operability by a user in a case of performing data transfer wirelessly in a near area, a near-field wireless communication circuit  10  included in a terminal  1 A is able to switch between a normal mode to perform OFDM and a near mode with a relatively short communicable distance as compared with that in the first communication mode and to perform spread spectrum. A controller  13  executes preliminary processing needed for initiating data transfer in the near mode with a terminal  1 B serving as a communication destination between the terminals  1 A and  1 B by using the near-field wireless communication circuit  10  which is set to the normal mode. Further, the controller  13  determines availability of the data transfer in the near mode with the terminal  1 B by using a measured value of communication quality which has a correlation with a communication distance to the terminal  1 B as a measure of the determination. Furthermore, when it is determined that the data transfer in the near mode is available, the controller  13  initiates the data transfer with the terminal  1 B by using the near-field wireless communication circuit  10  which is set to the near mode, based on a result of the preliminary processing executed in the normal mode in advance.

TECHNICAL FIELD

The present invention relates to a technique for transferring data between wireless communication devices which conduct near-field wireless communication.

BACKGROUND ART

There has been known a technology for the near-field wireless communication, the communicable distance of which is from several meters to several tens of meters. For example, Wireless USB (Wireless USB Specification Revision 1.0) targets at a communication distance of about 10 meters. The Wireless USB assumes that a transmission rate is 480 Mbit/s at the communication distance of 3 meters, and that the transmission rate is 110 Mbit/s at the communication distance of 10 meters.

The Wireless USB adopts UWB (ultra Wide Band) as a wireless platform at a physical layer. The UWB uses a wide band from 3.1 GHz to 10.6 GHz, and achieves a transmission rate of several hundred Mbit/s or higher at a short distance within a 20 meter radius. As modulation methods for the UWB, there have been proposed an impulse wireless method, an MB-OFDM (MultiBand-Orthogonal Frequency Division Multiplexing) method, a DS (Direct Sequence)-UWB method for performing direct spreading by PSK modulation, and the like. Communication devices using the MB-OFDM UWB method are disclosed in e.g. Patent Literatures 1 and 2. A communication device using the impulse wireless method is disclosed in e.g. Patent Literature 3. Further, a communication device which selectively uses OFDM communication and spread spectrum communication such as DS-UWB is disclosed in e.g. Patent Literature 4.

Recently, there has been also proposed a wireless communication method where the communicable distance is confined to a near area of about several centimeters. For example, TransferJet is a wideband wireless communication method where a near area within 3 centimeters is assumed as the communicable distance. According to a statement issued by TransferJet consortium proposing the TransferJet (http://www.transferjet.org/en/index.html), the TransferJet uses a microwave band (central frequency 4.48 GHz). The average transmitted power is equal to or lower than −70 dBm/MHz, and the maximum transmission rate is 560 Mbit/s at the communication distance within 3 centimeters.

CITATION LIST Patent Literature [Patent Literature 1]

-   International Patent Publication No. WO2008/056616

[Patent Literature 2]

-   Japanese Unexamined Patent Application Publication No. 2007-258904

[Patent Literature 3]

-   Japanese Unexamined Patent Application Publication No. 2007-318325

[Patent Literature 4]

-   Japanese Unexamined Patent Application Publication No. 2007-097186

SUMMARY OF INVENTION Technical Problem

In a case of applying a wireless communication method such as the TransferJet where the communication distance is limited to the near area of several centimeters to a mobile terminal (e.g., mobile phone or PDA (Personal Digital Assistance)), there is caused a new problem that it is difficult for a user to perform input operation for the mobile terminal or a destination device (e.g., PC (Personal Computer) or kiosk terminal) while maintaining a state where the mobile terminal can communicate with the destination device.

As an example, assume a case where content is downloaded from the kiosk terminal to the mobile terminal. In this case, there is conceivable a case where preliminary processing with the input operation by the user should be performed, while maintaining a state where it is possible to conduct communication between the kiosk terminal and the mobile terminal. The preliminary processing refers to for example, mutual authentication between the terminals, input of user information, approval of a condition for using content, a selection of content to be downloaded, and processing for electronic payment. In a case where the user performs input operation on the preliminary processing for the mobile terminal, it is necessary for the user to perform the input operation while the user moves the mobile terminal closer to the kiosk terminal. Therefore, operability may be deteriorated. Further, in a case where the user performs input operation on the preliminary processing for the kiosk terminal, it is not preferable in terms of security to put the mobile terminal in a position away from the user who is working on the input, even for maintaining the state where it is possible to conduct communication between the kiosk terminal and the mobile terminal. Therefore, it is necessary to give special attention to the layout of a wireless communication circuit in the kiosk terminal, the design of a chassis, and the like.

The present invention has been made in view of the above-mentioned problems, and aims to improve operability by a user in a case of performing data transfer wirelessly in a near area.

Solution to Problem

A wireless communication device according to a first exemplary aspect of the present invention includes a near field wireless communication circuit capable of switching between a first communication mode to perform OFDM and a second communication mode with a relatively short communicable distance as compared with that in the first communication mode and to perform spread spectrum, and a control unit controlling the switching between the first and second communication modes. The control unit executes, with a destination device through the near field wireless communication circuit that is set to the first communication mode, preliminary processing needed for initiating data transfer in the second communication mode with the destination device. Further, the control unit determines availability of the data transfer in the second communication mode with the destination device by using a measured value of communication quality related to a communication distance to the destination device as a measure of the determination. Furthermore, the control unit initiates, when it is determined that the data transfer is available, the data transfer by using the near field wireless communication circuit that is set to the second communication mode, based on a result of the preliminary processing.

Advantageous Effects of Invention

According to the first exemplary aspect of the present invention, preliminary processing involving user's input operation can be performed using the near-field wireless communication circuit that is set to the first communication mode. The first communication mode has a longer communicable distance as compared with that in the second communication mode, which is a mode to perform the data transfer in the near area. Thus, it is not necessary for the user to bring the wireless communication device very close to the destination device upon performing the preliminary processing. It is thereby possible to improve the operability by the user in the case of performing the data transfer wirelessly in the near area.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a configuration diagram of a wireless communication system according to a first exemplary embodiment of the present invention;

FIG. 2 is a block diagram showing a configuration example of each of terminals shown in FIG. 1;

FIG. 3 is a block diagram showing a configuration example of a near-field wireless communication circuit shown in FIG. 2;

FIG. 4A is a diagram showing one example of a method of performing switching between a normal mode and a near mode;

FIG. 4B is a diagram showing another example of the method of performing the switching between the normal mode and the near mode;

FIG. 5 is a sequence diagram on data transfer processing between the terminals shown in FIG. 1;

FIG. 6 is a sequence diagram showing one example of preliminary processing which is included in the data transfer processing shown in FIG. 5;

FIG. 7 is a sequence diagram showing another example of the preliminary processing which is included in the data transfer processing shown in FIG. 5;

FIG. 8 is a diagram showing an arrangement example of the terminals for explaining determination of the availability of the near mode;

FIG. 9 is a diagram showing an example of transmission data from the terminal which is located in a normal mode communication area in FIG. 8;

FIG. 10 is a diagram showing an example of transmission data from the terminal which is located in an intermediate area in FIG. 8;

FIG. 11 is a diagram showing one example of transmission data from the terminal which is located in a near area in FIG. 8;

FIG. 12 is a diagram showing another example of the transmission data from the terminal which is located in the near area in FIG. 8;

FIG. 13 is a sequence diagram on data transfer processing in a wireless communication system according to a second exemplary embodiment of the present invention;

FIG. 14 is a configuration diagram of a wireless communication system according to a third exemplary embodiment of the present invention;

FIG. 15 is a block diagram showing a configuration example of a terminal shown in FIG. 14;

FIG. 16 is a sequence diagram on data transfer processing between terminals shown in FIG. 14;

FIG. 17 is a sequence diagram showing an example of preliminary processing which is included in the data transfer processing shown in FIG. 16;

FIG. 18 is a sequence diagram on data transfer processing in a wireless communication system according to a fourth exemplary embodiment of the present invention;

FIG. 19 is a sequence diagram showing an example of preliminary processing which is included in the data transfer processing shown in FIG. 18;

FIG. 20 is a configuration diagram of a wireless communication system according to a fifth exemplary embodiment of the present invention;

FIG. 21 is a sequence diagram on data transfer processing between terminals shown in FIG. 20;

FIG. 22 is a sequence diagram showing an example of preliminary processing which is included in the data transfer processing shown in FIG. 21;

FIG. 23 is a configuration diagram of a wireless communication system according to a sixth exemplary embodiment of the present invention;

FIG. 24 is a sequence diagram on data transfer processing between terminals shown in FIG. 23; and

FIG. 25 is a sequence diagram showing an example of preliminary processing which is included in the data transfer processing shown in FIG. 24.

FIG. 26 is a block diagram showing a detailed configuration example of a receiving unit of an AFE 100;

FIG. 27 is a block diagram showing a detailed configuration example of an ADC 101;

FIG. 28A is a diagram showing operation in an MB-OFDM method;

FIG. 28B is a diagram showing operation in a DS-SS method;

FIG. 29 is a diagram showing operation in the DS-SS method;

FIG. 30 is a diagram showing operation in the DS-SS method;

FIG. 31 is a diagram showing operation in the DS-SS method;

FIG. 32 is a block diagram showing a configuration example of each of terminals shown in FIG. 1; and

FIG. 33 is a block diagram showing a configuration example of each of terminals shown in FIG. 1.

DESCRIPTION OF EMBODIMENTS

Hereinafter, specific exemplary embodiments to which the present invention is applied will be described in detail with reference to the drawings. The same signs are assigned to the same elements throughout the drawings, and their duplicated explanation is omitted as appropriate for clarifying the description.

First Exemplary Embodiment of the Invention

FIG. 1 shows configuration of a wireless communication system according to this exemplary embodiment. The wireless communication system according to this exemplary embodiment includes terminals 1A and 1B which conduct near-field wireless communication. Each of the terminals 1A and 1B can switch its operation mode between a normal mode for conducting the near-field wireless communication (e.g., within about 10 meters) and a near mode for conducting wireless communication in a nearer area (e.g., within several centimeters) as compared with that in the normal mode.

FIG. 2 is a block diagram showing a configuration example of each of the terminals 1A and 1B. In FIG. 2, a near-field wireless communication circuit 10 is a wireless interface for conducting the near-field wireless communication with another terminal (1A or 1B). The near-field wireless communication circuit 10 acquires transmission data from a memory, and outputs to an antenna 11 a transmission signal obtained by performing various processes such as generation of MAC (Media Access Layer) frames, modulation, D/A conversion, frequency conversion, and signal amplification. Further, the near-field wireless communication circuit 10 inputs therein a wireless signal received by the antenna 11, and stores in a memory 12 reception data obtained by performing various processes such as signal amplification, frequency conversion, A/D conversion, and demodulation.

Further, the near-filed wireless communication circuit 10 operates in at least two modes (normal mode and near mode) whose transmission rates and transmission rates are different with each other. The normal mode is an operation mode for conducting the near-field wireless communication (e.g., within about 10 meters). On the other hand, the near mode is an operation mode for conducting the wireless communication in the nearer area (e.g., within several centimeters) as compared with that in the normal mode.

Described next is a specific example of switching between the normal mode and the near mode. For example, in a case where the near-field wireless communication circuit 10 is a communication circuit that selectively performs MB-OFDM UWB communication and direct sequence spread spectrum (DS-SS: Direct Sequence Spread Spectrum) communication, wireless parameters in the normal mode and the near mode may be set respectively as shown in FIGS. 4A and 4B. FIG. 4A shows an example of the wireless parameters in the normal mode. On the other hand, FIG. 4B shows an example of the wireless parameters in the near mode. In FIGS. 4A and 4B, each transmission frame 40 indicates the one generated at a MAC layer in the UWB. The transmission frame 40 includes a preamble and a header 41, and a payload 42.

In the example of the normal mode shown in FIG. 4A, multi-channel transmission in the OFDM is performed by using a plurality of subcarriers which are included in one sub-band f1 (528 MHz width) in a band from 3.1 GHz to 10.6 GHz. In the normal mode, there is set a relatively high transmitted power density as compared with that in the near mode. For example, as shown in FIG. 4A, the transmitted power density may be controlled in order that the average transmitted power may become equal to or lower than −41.3 dBm/MHz. Further, in the normal mode, frequency hopping may be performed between plural sub-bands f1, f2 and f3, which belong to the same band group. A specific example of such a UWB communication circuit is disclosed in detail in the patent application (Patent Literature 1) which has been previously made by one of inventors of this application.

In the example in FIG. 4B, the near mode communication in the DS-SS method is performed. In the near mode, there is set a lower transmitted power density than that in the normal mode. For example, as shown in FIG. 4B, the transmitted power density may be controlled in order that the average transmitted power may become equal to or lower than −70 dBm/MHz. Thus, the communicable distance can be confined to the near area (e.g., within several centimeters). Further, if the power is equal to or lower than −70 dBm/MHz, it can be freed from legal restrictions for UWB, and any of a band of 500 MHz or lower and a band of 500 MHz or higher is selectable. A typical UWB is required to have a band of 500 MHz or higher. A specific example of the communication circuit using the DS-SS is disclosed in detail in the patent application (Japanese patent application No. 2007-261982, filed on Oct. 5, 2007 and Japanese patent application No. 2008-037671, filed on Feb. 19, 2008) which have been previously made by the applicant of the present application.

FIG. 3 is a block diagram of the near-field wireless communication circuit 10 in a case of adopting two communication methods: the MB-OFDM method and the DS-SS method. An analog front end (AFE) 100 performs frequency conversion (up-converting) and signal amplification for a transmission signal output from a D/A converter (DAC) 109, and thus outputs the obtained wireless signal to the antenna 11. Further, the AFE 100 performs signal amplification and frequency conversion (down-converting) for the wireless signal received by the antenna 11, and thus outputs the obtained baseband signal or IF (Intermediate Frequency) signal to an A/D converter (ADC) 101.

The ADC 101, an FFT unit 102, a de-modulator 103 and a decoder 104 are processing circuits for the received signal. The ADC 101 performs digital sampling for the received signal. The FFT unit 102 performs FFT operation for the received signal after sampling to perform demodulation of OFDM, which is the primary modulation. The de-modulator 103 restores transmission data from received symbols (information on phases and amplitude) of each subcarrier obtained by the FFT operation (the secondary demodulation), and performs parallel-serial conversion for the transmission data to be output to the decoder 104. The decoder 104 performs descrambling, error correction and the like for data column restored by the de-modulator 103, and then outputs it to a MAC unit 105.

The MAC unit 105 performs generation and decomposition of UWB MAC frames, and MAC layer control. A coder 106, a modulator 107, an IFFT unit 108 and the DAC 109 on the transmission side perform inverse processing to the above-mentioned processing units on the reception side (ADC 101, FFT unit 102, de-modulator 103 and decoder 104).

FIG. 32 is a diagram showing in detail operation of each element of the near-field wireless communication circuit 10 when processing an MB-OFDM signal. The ADC 101 operates at a high resolution of about six bits. The OFDM signal has a feature that the communication distance is relatively long and equalization can be performed with a relatively simple configuration even in an environment where fading occurs significantly. On the other hand, the resolution of the ADC 101 needs to be relatively high. By the high-resolution operation of the ADC 101 during the OFDM signal processing, it is possible to perform equalization and minimize the effect of fading. A specific detail of the equalization may be equalization of a symbol as a whole using a channel estimation symbol, real-time equalization using a pilot tone contained in each symbol, equalization of a delayed wave using a cyclic prefix and the like.

In the MB-OFDM method, the DAC 109 also provides a higher resolution of about six bits. This is because it is necessary to form a transmission signal within a target quantization error in order to send signals multiplexed in the frequency domain in a time-series manner.

In the MB-OFDM method, the de-modulator 103 performs demodulation of a QPSK signal or a 16QAM signal, which is the secondary modulation of each OFDM tone, to be more specific. The modulator 107 performs modulation of those signals.

FIG. 33 is a diagram showing in detail operation of each element of the near-field wireless communication circuit 10 when processing a DS-SS signal. The ADC 101 operates at a low resolution of about two bits. The effect of fading is minor if the communicable distance is limited to relatively short. Therefore, rake processing or DFE (Decision feedback equalizer) processing, which is equalization for the DS-SS, can be eliminated, and the resolution of the ADC 101 can be reduced. Because there is no multiplexing in the frequency domain in the DS-SS method, the DAC 109 may also operate at a low resolution of about two bits. In some configurations, the DAC 109 may be eliminated, and a spread signal may be obtained directly from a logic signal. In such a case, the operation of the DAC 109 may be suspended during the DS-SS communication. Because the FFT 102 and the IFFT 108 are not used in the DS-SS method, the operation of those is suspended.

During the DS-SS communication, the modulator 107 performs modulation operation such as QPSK and spread operation using pseudo-random codes. The spread operation may use direct spreading that directly multiplies a modulated signal by a Barker code and the like. It may use MBOK (M-ary Bi-orthogonal Keying) that prepares a plurality of pseudo-random codes and represents information by which code is transmitted. The de-modulator 103 performs demodulation operation (inverse-spread operation) of such spread signals using a matched filter and the like.

In the configuration examples shown in FIGS. 3, 31 and 32, it is possible to acquire, as information on communication quality of the received signal, an RSSI (Received Signal Strength Indicator) which can be obtained in the AFE 100 or the ADC 101, an LQI (Link Quality Indicator) which can be obtained in the de-modulator 103, and a bit error rate (BER) which can be obtained in the decoder 104. The information on communication quality relates to a communication distance to a destination device, and thus can be used for determining the availability of communication in the near mode with the destination device. Details about the determination of the availability of the communication in the near mode by use of the information on communication quality will be described later.

Hereinbefore, there have been described the specific examples of the configuration of the near-field wireless communication circuit 10 shown in FIG. 2 and the switching of the operation mode. Note that it is obvious that each switching of the operation mode shown in FIGS. 4A and 4B is no more than an example. For example, the data transmission rate may be modified by changing the modulation method (e.g., between binary modulation and multilevel modulation), a baud rate, or the number of channels by MIMO (Multiple-Input Multiple-Output). Further, the normal mode of the near-field wireless communication circuit 10 is not limited to the MB-ODM method but may be OFDM in another method. Further, the near mode may be another spread spectrum communication such as impulse wireless, carrier-based pulse wireless, or DS-UWB.

Returning to FIG. 2, the description is continued. The memory 12 stores transmission and reception data of the near-field wireless communication circuit 10, image data to be output to a display unit 14 which will be described later, a computer program to be executed by a controller 13, and the like. Note that the memory 12 shown in FIG. 2 represents a logical structural unit. That is, the memory 12 is made by a combination of a ROM (Read Only Memory), a RAM (Random Access Memory), a flash memory, and the like.

The controller 13 performs overall control in the terminal 1 (1A or 1B), and controls data transfer with the near-field wireless communication circuit 10 with a different terminal. Mentioned in more detail, the controller 13 performs execution control for preliminary processing which is executed in the normal mode between the terminal 1 and the different terminal in advance of data transmission in the near mode. Further, the controller 13 controls switching from the normal mode to the near mode and the initiation of data transfer in the near mode, based on a measurement result of communication quality with the different terminal. Details about the preliminary processing will be described later.

The display unit 14 includes a display device such as an LCD (Liquid Crystal Display) or an organic EL (Electro-Luminescence) display, and thus outputs a message or the like generated by the controller 13.

An operation accepting unit 15 includes input devices such as operation buttons, a keyboard and a touch panel, and thus accepts input operation by a user of the terminal 1.

Hereinafter, data transfer processing in the near mode, which is executed between the terminals 1A and 1B, will be described in detail. FIG. 5 is a sequence diagram showing the data transfer processing executed between the terminals 1A and 1B. Note that in FIG. 5, the terminal 1A serves as the reception side upon data transfer in the near mode, and the terminal 1B serves as the transmission side.

At Step S101, the terminals 1A and 1B are connected to each other in the normal mode by using the respective near-field wireless communication circuits 10, based on the control by the controller 13 included in each of the terminals 1A and 1B. At Step S102, the terminals 1A and 1B execute, in the normal mode, preliminary processing on data transfer in the near mode to be performed later. The preliminary processing is executed with at least one of the input operation by the user to the operation accepting unit 15 in at least one of the terminals 1A and 1B, and displaying the message to the user by the display unit 14 in at least one of the terminals 1A and 1B. For example, the preliminary processing includes at least one of (a) checking vacancy in the memory for reception of the terminal 1A from the terminal 1B and displaying a result of the check to the user, (b) removing data from the memory for reception of the terminal 1A in response to the input operation by the user to the terminal 1A or 1B, (c) designating, by the user, content to be transferred in the near mode from the terminal 1B to the terminal 1A, (d) making electronic payment with the input operation by the user to the terminal 1A or 1B, and (e) authenticating a communication destination terminal (1A or 1B) with the input operation by the user to the terminal 1A or 1B.

Specific examples of the preliminary processing will be described by using sequence diagrams in FIGS. 6 and 7. FIG. 6 indicates a procedure where the user operates the terminal 1B serving as the data transmission side, thereby checking the availability of reception at the terminal 1A serving as the data reception side. At Step S201, the terminal 1B acquires directory information of the terminal 1A. At Step S202, the terminal 1B acquires a free space on the memory 12 included in the terminal 1A.

At Step S203, the display unit 14 in the terminal 1B displays the directory information and the free space on the memory of the terminal 1A. Then, the controller 13 in the terminal 1B acquires an instruction to transfer data from the terminal 1B to the terminal 1A by the input operation by the user to the operation accepting unit 15. The controller 13 in the terminal 1B transmits an instruction to receive the data to the terminal 1A through the near-field wireless communication circuit 10, in response to the acquisition of the instruction to transfer the data (Step S204). The terminal 1A, which has received the instruction to receive the data, prepares for receiving the data by activating an application program for receiving the data, or the like.

At Step S205, the controller 13 in the terminal 1B transmits an instruction to perform the determination of the availability of the near mode to the terminal 1A through the near-field wireless communication circuit 10. The determination of the availability of the near mode is a process to determine whether the terminals 1A and 1B are located in the near area where it is possible to transfer the data in the near mode. At Step S206, in order to be able to transfer the data in the near mode, the display unit 14 in the terminal 1B displays a message for prompting the user to perform operation (touch operation) to move one of the terminals 1A and 1B closer to another. Note that the message for prompting the touch operation may be displayed by the display unit 14 in the terminal 1A.

Another example of the preliminary processing is described by using FIG. 7. FIG. 7 indicates a procedure where the user operates the terminal 1A serving as the data reception side, thereby selecting content to be acquired from the terminal 1B serving as the data transmission side. At Step S301, the terminal 1A acquires information on content (name of content, creator, created date and time, data size, price, and the like) held by the terminal 1B. At Step S302, the display unit 14 in the terminal 1A displays the information on content acquired from the terminal 1B. Then, the controller 13 in the terminal 1A accepts a selection of content to be transferred by the input operation by the user to the operation accepting unit 15.

At Step S303, the controller 13 in the terminal 1A transmits, to the terminal 1B through the near-field wireless communication circuit 10, an instruction to transmit the selected content. The terminal 1A, which has transmitted the instruction to transmit the content, prepares for receiving data by activating an application program for receiving the data, or the like. At Step S304, the controller 13 in the terminal 1B transmits the instruction to perform the determination of the availability of the near mode to the terminal 1A through the near-field wireless communication circuit 10. At Step S305, the terminal 1A, which has received the instruction to perform the determination of the availability of the near mode, displays a message for prompting the user to perform the touch operation. Note that the message for prompting the touch operation may be displayed by the display unit 14 in the terminal 1B.

Returning to FIG. 5, Step S103 and the subsequent Steps are described. At Step S103, in order to determine the availability of the near mode, the terminal 1B transmits a wireless signal to the terminal 1A. At Step S104, the terminal 1A performs determination of the availability of data reception in the near mode. The determination may be performed by using reception quality in the terminal 1A of the wireless signal transmitted from the terminal 1B. Specific examples of the determination will be described later.

When it is determined that the data reception in the near mode is unavailable at Step S104, the terminal 1A displays a message for the user (Step S105). For example, the message may be the one for continuously prompting the touch, the one indicating out of the near mode, the one indicating a degree of closeness of the terminals 1A and 1B, or the like. Further, an image may be displayed as a substitute for displaying the message or by combining it therewith. Further, the display may be performed by LEDs (Light Emitting Diodes) as a substitute for displaying the message or by combining them. For example, the degree of closeness of the terminals 1A and 1B may be indicated by the number of lighted LEDs, the color of a lighted LED, or the like. Furthermore, the display of the message at Step S105 may be performed by the display unit 14 in the terminal 1B.

On the other hand, when it is determined that the data reception in the near mode is available at Step S104, the terminals 1A and 1B are connected to each other in the near mode (Step S106). Finally, at Step S107, the terminals 1A and 1B perform the data transfer in the near mode.

Hereinafter, specific examples of the determination of the availability of the near mode will be described by using FIGS. 8 to 12. FIG. 8 is a diagram showing an arrangement example of the terminals for explaining the determination of the availability of the near mode. As shown in FIG. 8, an area (e.g., within about 10 meters) where it is possible to conduct communication in the normal mode but it is not possible to conduct communication in the near mode is referred to as “normal mode communication area”. Further, an intermediate area between the “normal mode communication area” and the “near area” where it is possible to perform the data transfer in the near mode is referred to as “intermediate area”.

Upon starting the determination of the availability of the near mode, the terminals 1A and 1B conduct communication in the normal mode. That is, the terminal 1A receives a wireless signal transmitted in the normal mode from the terminal 1B, and measures reception quality of this wireless signal. FIG. 9 is a diagram showing transmission signals from the terminals 1A and 1B in the “normal mode communication area”. Note that FIG. 9 shows an example in a case where the near-field wireless communication circuit 10 serves as the communication circuit capable of MB-OFDM and DS-SS communication. As shown in FIG. 9, the terminals 1A and 1B mutually transmit beacon signals 71 and 72, and thus establish synchronization of a superframe. The superframe is a transmission frame prescribed by the UWB MAC, and one superframe period is 65.536 msec. The superframe is divided into 256 MASs (Medium Access Slots). One MAS period is 256 μsec. The beginning part of the superframe is assigned as a period (referred to as Beacon Period) for transmitting the beacon signal which is used for establishing the synchronization of the superframe and for transferring various control signals. Each of the beacon signals 71 and 72 includes a preamble 73, a header 74, and a payload 75. In FIG. 9, “BP” indicates the Beacon Period, and “DP” indicates Data Period.

In the normal mode communication area, the terminal 1A receives the beacon signal 71 transmitted from the terminal 1B, and measures reception quality of the beacon signal 71. As the reception quality of the beacon signal 71, an RSSI of the preamble 73 and an RSSI of the payload 75 may be measured. Note that the measurement of the reception quality may be performed with respect not only to any one of the above-mentioned RSSI, LQI and BER, but to two or more measures. In this exemplary embodiment, a distance (degree of closeness) between the terminals 1A and 1B is determined by using measured values of the reception quality such as the RSSI, the LQI and the BER as measures. It can be generally judged that the distance between the terminals 1A and 1B becomes shorter as the RSSI become higher. However, in a case of measuring noise power, there is decreased a correlation between the RSSI and the distance (degree of closeness) between the terminals 1A and 1B. Further, although the BER is generally improved when the distance between the terminals gradually becomes shorter, the BER deteriorates in contrast when the distance between the terminals is so short that it exceeds a dynamic range of the terminal on the reception side. Therefore, for example, measurement of the BER after decoding and measurement of the RSSI may be used together.

FIG. 10 is a diagram showing transmission signals from the terminals 1A and 1B in the “intermediate area”. In the intermediate area, the terminals 1A and 1B transmit the beacon signals 71 and 72 in the normal mode. Further, the terminal 1B transmits a wireless signal 76 in the near mode by using the MAS other than that during the Beacon Period. At this time, a transmission timing of the wireless signal 76 in the near mode may be designated by the beacon signal 71.

As shown in FIG. 10, the beacon signals 71 and 72 are transmitted in the normal mode. Thus, there is a low possibility that each of the terminals 1A and 1B fails in the reception of the beacon signal, so that the synchronization of the superframe can be maintained. Further, the transmission timing of the wireless signal 76 is notified by using the beacon signal transmitted in the normal mode. Thus, the transmission timing can be reliably transmitted to the terminal 1A. Therefore, it is not necessary for the terminal 1A to perform reception operation for long periods of time. Further, it takes a short period of time for the wireless signal 76 to occupy the superframe. Thus, it is possible to secure time when another terminal can perform the data transfer.

In the example shown in FIG. 10, the terminal 1A may determine the degree of closeness of the terminals 1A and 1B by measuring the reception quality of the beacon signal 72 transmitted in the near mode.

FIG. 11 is a diagram showing transmission signals from the terminals 1A and 1B in the “near area”. In the example in FIG. 11, the terminals 1A and 1B transmit the beacon signals 71 and 72 in the normal mode also in the near area. It is possible to notify the presence of the terminals 1A and 1B to a different terminal which is located around the terminals 1A and 1B, by continuing the transmission of the beacon signal in the normal mode as shown in FIG. 11. Therefore, it is possible to prevent occurrence of such a problem that the MAS for transmitting the beacon signal collides with that for the neighboring terminal.

Further, the terminal 1B transmits a wireless signal 77 in the near mode by using the MASs other than those during the Beacon Period. The wireless signal 77 is a signal which includes transmission data from the terminal 1B to the terminal 1A. There is reduced overhead (time not contributing to the data transmission) by using the MASs other than those during the Beacon Period within the superframe as much as possible for the data transmission in the near mode, so that it is possible to improve an effective data transmission rate.

FIG. 12 is a diagram showing another example of the transmission signals from the terminals 1A and 1B in the “near area”. In the example in FIG. 12, the beacon signals 71 and 72 are transmitted in the near mode. Thus, the beacon signals 71 and 72 cannot be detected by a terminal other than the terminals 1A and 1B which are located in the near area. Therefore, it is possible to further lower a possibility that the wireless signal 77 which includes the data signal is sniffed.

By the way, FIGS. 9 to 12 show examples where the measurement of the reception quality in the normal mode and that in the near mode are used together upon performing the determination of the availability of the near mode. Thus, the terminal 1A can continuously measure the reception quality at the whole range of the normal mode operation area, the intermediate area, and the near area. Therefore, the terminal 1A can properly display the degree of closeness of the terminals 1A and 1B at the whole range of the normal mode operation area, the intermediate area, and the near area. Further, the final determination of the availability is performed based on the reception quality in the near mode. Therefore, it is possible to improve accuracy of the determination. Meanwhile, measurement of the reception quality may be performed in only one of the normal mode and the near mode at the whole range of the normal mode operation area, the intermediate area and the near area, and the determination of the availability of the near mode may be performed based on a result of this measurement.

As mentioned above, the wireless communication system according to this exemplary embodiment performs, in the normal mode, the preliminary processing to be executed between the terminals 1A and 1B in advance of the data transfer in the near mode. Thus, it is not necessary for the user to bring one of the terminals 1A and 1B very close to the other upon performing the preliminary processing. Accordingly, it is possible to improve the operability by the user in a case of performing the data transfer wirelessly in the near area.

Further, the wireless communication system according to this exemplary embodiment performs the preliminary processing by use of the OFDM method with strong equalization and enabling relatively long distance communication and performs data transfer in near proximity by use of the DS-SS method allowing a decrease in resolution of the ADC 101 and the DAC 109 and enabling reduction of power consumption, and it is thereby possible to reduce power consumption of each terminal as well as improving the operability by the user.

Note that in the above-mentioned description, there is shown the examples where the wireless signal is transmitted by the terminal 1B and received by the terminal 1A upon the determination of the availability of the near mode. Meanwhile, the wireless signal may be transmitted by the terminal 1A and received by the terminal 1B. Further, the signal transmission and reception upon the determination of the availability of the near mode may be bidirectionally performed.

Specific Embodiment Related to the First Exemplary Embodiment

FIG. 26 shows a detailed configuration example of a receiving unit of the AFE 100. The AFE 100 in FIG. 26 includes a low noise amplifier 2601, a quadrature mixer 2602, a local (LO) signal generator 2603, a complex filter 2604, a low pass filter 2605, and a variable gain amplifier 2606.

An OFDM signal or a DS-SS signal input to the antenna 11 is amplified by the low noise amplifier 2601 and down-converted to a baseband signal by the quadrature mixer 2602. The LO signal generator 2603 generates a LO signal necessary for the down conversion. A necessary band is extracted from the baseband signal by the complex filter 2604, and then a high-frequency noise and a high-frequency spurious wave are removed by the low pass filter 2605. The variable gain amplifier 2606 amplifies the baseband signal up to the level necessary for execution of sampling by the ADC 101.

FIG. 27 shows a detailed configuration example of the ADC 101. The ADC 101 in FIG. 27 includes a ladder resistor 2704 and a comparator unit 2705. The ladder resistor 2704 divides a voltage between a higher reference voltage 2702 and a lower reference voltage 2703 at regular intervals. The comparator unit 2705 includes a plurality of comparators. As an example, the total number of the comparators is 64. Each of the 64 comparators compares a voltage signal divided by the ladder resistor 2704 with an input signal supplied from an input signal terminal 2701. The number of comparators to operate simultaneously is varied according to a signal input to a resolution switching terminal 2706. In the normal mode when the OFDM signal is received, a signal indicating the high-resolution operation is input to the resolution switching terminal 2706. Further, in the near mode when the DS-SS signal is received, a signal indicating the low-resolution operation is input to the resolution switching terminal 2706.

In the case of performing the high-resolution operation of about six bits in accordance with the normal mode, for example, the resolution switching terminal 2706 is controlled so that the 64 comparators included in the comparator unit 2705 operate. In the case of performing the low-resolution operation of about two bits in accordance with the near mode, for example, the resolution switching terminal 2706 is controlled so that only four of the comparators included in the comparator unit 2705 operate. Note that, in the low-resolution operation, four comparators corresponding to four voltage signals at regular intervals may operate. For example, the 1st, 22nd, 43rd and 64th comparators from the top of FIG. 27 may operate. Thus, at the high-resolution of six bits, an input signal to the comparator unit 2705 is compared with each of the voltages divided into 64 levels by the ladder resistor 2704. On the other hand, at the low-resolution of two bits, the input signal is compared with each of the voltages divided into four levels by the ladder resistor 2704.

FIGS. 28A and 28B are diagrams showing operation of switching the passband of the complex filter 2604. FIG. 28A shows the operation when receiving the MB-OFDM signal, and FIG. 28B shows the operation when receiving the DS-SS signal. In the examples of FIGS. 28A and 28B, the number of LO frequency is one, and the LO frequency is set to a center frequency of a carrier band of the MB-OFDM signal and the DS-SS signal.

In FIG. 28A, the complex filter 2604 periodically switches among a negative frequency pass (−f Pass), all pass (All Pass), and a positive frequency pass (+f Pass) in order to be compatible with frequency hopping performed in the MB-OFDM method. When receiving a symbol A located in the negative frequency compared with the LO frequency, the complex filter 2604 lets the symbol A pass as the negative frequency pass. When receiving a symbol B existing across the LO frequency, the complex filter 2604 lets the symbol B pass as the all pass. When receiving a symbol C located in the positive frequency compared with the LO frequency, the complex filter 2604 lets the symbol C pass as the positive frequency pass. Only one of the symbol A and the symbol C, which are in relation of image frequency, can be thereby selected. Although it has been necessary to generate a plurality of LO frequencies in order to receive the symbols A to C at fast hopping, reception operation can be performed only with one LO frequency which is set to near the center of a plurality of symbols in this configuration. The same applies to transmission operation.

Although fast frequency hopping is usually not adopted in the DS-SS method shown in FIG. 28B, there may be a case where a plurality of bands are switched in a time division manner. In such a case, signal reception can be performed only with one LO frequency by sequentially switching the passband of the complex filter 2604. Note that there may be, of course, a case where frequency hopping is performed in the DS-SS method also in order to obtain the frequency diversity effect. In such a case, it is adaptable by switching the passband of the complex filter 2604 fast in the same manner as the MB-OFDM method shown in FIG. 28A.

Use of the complex filter 2604 allows the ADC 101 to perform under-sampling operation and thereby reduces the sampling rate. As shown in FIGS. 28A and 28B, it is assumed that, at the time of receiving the symbol C, for example, the Nyquist frequency (fN) of the ADC 101 is at the center frequency of the symbol C. In this case, the right half of the symbol C is located outside the Nyquist frequency range as a matter of course. However, by the folding (aliasing) effect of the ADC 101, the right half of the symbol C is folded to the negative frequency side of the LO frequency (within the Nyquist frequency range). A spurious wave such as the symbol A which has existed in the frequency domain has been already suppressed by the complex filter 2604. There is thus no need to use the ADC 101 that fully covers the symbols A and C to their ends as the Nyquist frequency, and the sampling rate can be reduced. For example, in the MB-OFDM method, the center frequency of the symbol C is separated from the LO frequency by 528 MHz, the Nyquist frequency of the ADC 101 can be 528 HMz, and the sampling rate can be 1056 MS/s. In the case of not using the complex filter 2604, the sampling rate of 1584 MS/s or higher that fully covers the symbol C is required.

FIG. 29 is an example in which a plurality of LO frequencies are provided to receive the DS-SS signal. In the case of not performing frequency hopping in the DS-SS method, it is not necessary to switch the LO frequency at high speed. Therefore, it is adaptable to the plurality of frequencies by providing one PLL (Phase Locked Loop) circuit in the LO signal generator 2603 and sequentially re-locking necessary frequencies. In this case, the sampling rate of the ADC 101 is 528 MS/s or higher, which allows conversion of one symbol.

FIG. 30 is a waveform chart related to a time waveform of the DS-SS signal and an example of its signal processing. (a) is the DS-SS signal, (b) is a local signal, (c) is a received signal waveform after down conversion in the quadrature mixer 2602, and (d) is a sampling signal of the ADC 101.

The DS-SS signal shown in the waveform (a) is generated by a carrier-based pulse wireless method. For example, a carrier frequency (fc) may be 7 GHz, a chip time (t0) may be 2 ns, a pulse repetition frequency (PRF) may be about 250 MHz. A spread spectrum signal with a band of about 500 MHz centered at 7 GHz can be thereby obtained. As a modulation method, BPSK modulation or QPSK modulation which changes the phase of a signal may be used. It is preferred to use a pseudo-random code in order to uniformly spread the spectrum in the band.

The frequency of the local signal shown in the waveform (b) equals the carrier frequency of the DS-SS signal (which is 7 GHz in this example). Thus, the waveform (C) after down conversion in the quadrature mixer 2602 is an envelope waveform of the DS-SS signal and is able to demodulate a modulated signal (chip-level demodulation). The sampling frequency (fclk) of the sampling signal (waveform (d)) of the ADC 101 may be 1 GS/s, for example. The ADC 101 can thereby sample the received signal after down conversion (waveform (c)).

FIG. 31 is a waveform chart when receiving the symbol C in the example of FIG. 29. Because the carrier frequency (fc) is located around 7.5 GHz, down conversion with the local frequency of 7 GHz (waveform (b)) gives a signal containing a high-frequency component like the waveform (c). By A/D conversion of this signal by the sampling signal with 1 GS/s (waveform (d)), demodulation of the chip and demodulation of the symbol can be performed in the digital region. One chip modulation method is to perform frequency conversion of the symbol C signal in the high frequency domain to near DC. Further, another method is to determine the phase of the signal based on the sequence to cross the threshold as is obvious from FIG. 31( c). In FIG. 31( c), the signal has a waveform convex to the above first, and then has a waveform convex to the below inside the chip. Demodulation of the chip may be performed by using that the sequence is reversed in some chips.

Second Exemplary Embodiment of the Invention

A wireless communication system according to this exemplary embodiment includes terminals 2A and 2B which conduct near-field wireless communication. At least one of the terminals 2A and 2B includes a function of searching a terminal which is compatible with the near mode (hereinafter, near mode-compatible terminal). Note that configuration of the terminals 2A and 2B may be similar to that of the terminals 1A and 1B described in the first exemplary embodiment of the invention. Further, a procedure of data transfer in the near mode between the terminals 2A and 2B may be similar to that between the terminals 1A and 1B, with the exception that the search of the near mode-compatible terminal is performed.

FIG. 13 is a sequence diagram showing processing for data transfer performed between the terminals 2A and 2B. Note that in FIG. 13, the terminal 2A serves as the reception side upon the data transfer in the near mode, and the terminal 2B serves as the transmission side. At Step S401, the terminal 2B searches near mode-compatible terminals. In order to enable the search of the near mode-compatible terminal, the terminal 2A transmits information indicating the near mode-compatible terminal. For example, in a case where the near-field wireless communication circuit 10 included in the terminal 2A is the UWB communication circuit capable of MB-OFDM and DS-SS communication, identification information which indicates the near mode-compatible terminal may be included in the header 74 or the payload 75 of the beacon signal 72 shown in FIG. 9. The terminal 2A may transmit the identification information which indicates the near mode-compatible terminal in response to a query signal from the terminal 2B, or may voluntarily transmit it at constant intervals.

At Step S402, the terminal 2B outputs information on a group of terminals found by the search to the display unit 14. Then, the terminal 2B accepts, by the operation accepting unit 15, operation for selecting a terminal to be wirelessly connected therewith among the group of terminals found by the search. At Step S101, the terminal 2B connects in the normal mode to the selected terminal (2A). Note that operation of the terminals 2A and 2B at Steps S101 to S107 in FIG. 13 may be similar to that of the terminals 1A and 1B at the corresponding Steps described in FIG. 5.

Third Exemplary Embodiment of the Invention

FIG. 14 shows configuration of a wireless communication system according to this exemplary embodiment. The wireless communication system according to this exemplary embodiment includes a mobile phone terminal 3A and a kiosk terminal 3B which conduct near-field wireless communication. As with the above-mentioned terminals 1A and 1B, each of the terminals 3A and 3B can switch its operation mode between the normal mode for conducting the near-field wireless communication (e.g., within about 10 meters) and the near mode for conducting the wireless communication in the nearer area (e.g., within several centimeters) as compared with that in the normal mode. The mobile phone terminal 3A performs acquisition of content and an encryption key (reproduction key) for reproducing the content from the kiosk terminal 3B by using the near mode. For example, the content is moving image data, still image data, or an application program which can be used in the mobile phone terminal 3A.

FIG. 15 is a block diagram showing a configuration example of the mobile phone terminal 3A. In FIG. 15, a mobile phone communication circuit 30 connects through an antenna 31 to a base station arranged in a mobile phone communication network. Other components shown in FIG. 15 may be similar to those shown in FIG. 2, and thus their duplicated explanation is omitted. Further, the configuration of the kiosk terminal 3B may be similar to that of each of the terminals 1A and 1B shown in FIG. 2.

Hereinafter, processing for data transfer in the near mode performed between the mobile phone terminal 3A and the kiosk terminal 3B will be described in detail. FIG. 16 is a sequence diagram showing the processing for the data transfer performed between the terminals 3A and 3B. Note that in FIG. 16, the mobile phone terminal 3A serves as the reception side upon data transfer in the near mode, and the kiosk terminal 3B serves as the transmission side.

At step S501 in FIG. 16, the mobile phone terminal 3A initiates the operation of the near-field wireless communication circuit 10. The operation of the near-field wireless communication circuit 10 may be initiated in response to operation by the user. The kiosk terminal 3B may be in an operating state where the near-field communication can be available constantly or periodically, in order to accept connection with the near mode-compatible terminal such as the mobile phone terminal 3A. At Steps S502 and S503, the terminals 3A and 3B mutually detect the opposite terminal.

At Step S101 in FIG. 16, the terminals 3A and 3B connect in the normal mode to each other by using the respective near-field wireless communication circuits 10, based on the control by the respective controllers 13 included therein. At Step S504, the terminals 3A and 3B perform, in the normal mode, preliminary processing on data transfer in the near mode (Step S107) which will be performed later.

FIG. 17 is a sequence diagram showing a specific example of the preliminary processing performed at Step S504. Note that in FIG. 17, processes at Steps S601 and S602 are added to the example of the preliminary processing shown in FIG. 7. At Step S601, the terminal 3A accepts selection operation of a method for payment by the user. For example, a method for paying the purchase price of the content may be selected from among electronic money payment and other methods for the payment (credit card, cash, or the like). Further, among plural pieces of electronic money, there may be selected the one for using the payment of the purchase price.

At Step S602, in a case where the payment by the electronic money is selected, the purchase price of the content is compared to balance of the electronic money, and thus it is checked whether or not the balance of the electronic money is sufficient. When the balance of the electronic money is sufficient (OK at Step S602), Step S303 and the subsequent Steps are carried out. On the other hand, when the balance of the electronic money is insufficient, the selection of the method for the payment may be accepted again by returning to Step S302.

Returning to FIG. 16, the description is continued. Operation of the terminals 3A and 3B at Steps S103 to S107 may be similar to that of the terminals 1A and 1B at the corresponding Steps described in FIG. 5. Note that at Step S107, content data held by the kiosk terminal 3B is transferred to the terminal 3A.

At Step S505, electronic payment processing is performed in the near mode between the terminals 3A and 3B. For example, in a case where information on remaining amount of the electronic money is stored in the memory 12 of the mobile phone terminal 3A, there may be performed a process to subtract the amount equivalent to the price of the content from the remaining amount of the electronic money held by the mobile phone terminal 3A. Further, there may be configured so that an external payment server (not shown) performs the payment processing. Specifically, user information, credit card information and the like, which are stored in the memory 12 of the mobile phone terminal 3A, may be transmitted from the mobile phone terminal 3A to the kiosk terminal 3B and transferred from the kiosk terminal 3B to the external payment server (not shown), and then the payment processing may be performed by the payment server (not shown). Further, the kiosk terminal 3B may receive notification indicating completion of the payment from the payment server, and may transfer the notification to the mobile phone terminal 3A.

At Step S506, under a condition where the payment processing is normally completed, the kiosk terminal 3B transmits the encryption key required for reproducing and executing the content to the mobile phone terminal 3A.

The wireless communication system according to this exemplary embodiment performs the delivery of the encryption key (reproduction key) for using the content in the near mode. In the near mode, the communicable range is limited. Therefore, the wireless communication system according to this exemplary embodiment can prevent the reproduction key from being leaked to a third person due to impersonation or eavesdropping. The wireless communication system according to this exemplary embodiment is available as a system for selling contents such as music data and video data, for example, by arranging the kiosk terminal in a store.

In the description mentioned above, it has been assumed that the terminal 3A is the mobile phone terminal. Meanwhile, the terminal 3A may be a different terminal such as a portable music and video player which includes a function of reproducing the content.

Further, the payment processing in FIG. 16 may be performed by a terminal for payment, which is different from the kiosk terminal 3B. In this case, the transfer of the reproduction key may be performed in the near mode between the terminal 3A and the terminal for payment. Further, the payment processing in FIG. 16 may be replaced by a normal payment with the credit card or the cash. In this case, the transfer of the reproduction key may be performed in the near mode between e.g. a POS (Point-of-Sale) register and the terminal 3A.

Fourth Exemplary Embodiment of the Invention

A wireless communication system according to this exemplary embodiment includes terminals 4A and 4B which conduct near-field wireless communication. The terminals 4A and 4B perform, in the near mode, exchange of a connection key associated with authentication of the opposite terminal. Note that configuration of the terminals 4A and 4B may be similar to that of the terminals 1A and 1B described in the first exemplary embodiment of the invention.

FIG. 18 is a sequence diagram showing processing for data transfer performed between the terminals 2A and 2B. At Steps S701 and S702, the terminals 4A and 4B initiate the operation of the respective near-field wireless communication circuits 10. At Steps S703 and S704, the terminals 4A and 4B mutually detect the opposite terminal.

At Step S101 shown in FIG. 18, the terminals 4A and 4B connect in the normal mode to each other by using the respective near-field wireless communication circuits 10, based on the control by the respective controllers 13 included therein. At Step S705, the terminals 4A and 4B perform, in the normal mode, preliminary processing on data transfer in the near mode (Step S707) which will be performed later.

FIG. 19 is a sequence diagram showing a specific example of the preliminary processing performed at Step S705. At Step S801, the terminal 4A displays on the display unit 14 detection of terminals (including the terminal 4B) which have not been authenticated. At Step S802, the terminal 4A accepts, through the operation accepting unit 15, operation for instructing to start authentication of the terminal 4B. At Step S304, the terminal 4A transmits an instruction signal for starting the determination of the availability of the near mode to the terminal 4B, in response to the instruction to start the authentication of the terminal 413. The terminal 4B, which has received the instruction signal, may start preparation for the signal transmission at Step S103. At Step S305, the terminal 4A outputs the message for prompting the touch to the display unit 14. Note that although FIG. 19 shows that Steps S801, S802 and S304 are performed by the terminal 4A, it is obvious that these processes may be performed by the terminal 4B.

Returning to FIG. 18, the description is continued. Operation of the terminals 4A and 4B at Steps S103 to S106 may be similar to that of the terminals 1A and 1B at the corresponding Steps described in FIG. 5.

At Step S706, the terminals 4A and 4B perform the exchange of connection key in the near mode. For this key exchange, a key-exchange algorithm such as a Diffie-Hellman method may be used. At Step S707, the terminals 4A and 4B perform data transfer in the near mode by using the connection key shared at Step S706 between the terminals 4A and 4B.

The wireless communication system according to this exemplary embodiment performs, in the near mode, the processing for authenticating the communication destination terminal to exchange the connection key. In the near mode, the communicable range is limited. Therefore, the wireless communication system according to this exemplary embodiment can prevent the connection key from being leaked to a third person due to impersonation or eavesdropping. Further, it is possible to complete the authentication of the communication destination terminal by the touch operation, which is intuitive and simple for the user. Note that it is obvious that the procedure of the terminal authentication described in this exemplary embodiment may be used by combining it with the above-mentioned first to third exemplary embodiments of the invention, or with fifth and sixth exemplary embodiments of the invention which will be described later.

Fifth Exemplary Embodiment of the Invention

FIG. 20 shows configuration of a wireless communication system according to this exemplary embodiment. The wireless communication system according to this exemplary embodiment includes mobile phone terminals 5A and 5B which conduct near-field wireless communication. As with the above-mentioned terminals 1A and 1B, each of terminals 5A and 5B can switch its operation mode between the normal mode for conducting the near-field wireless communication (e.g., within about 10 meters) and the near mode for conducting wireless communication in the nearer area (e.g., within several centimeters) as compared with that in the normal mode. The terminal 5B can execute an application program (mailer) for e-mail transmission and reception. Upon transmitting an e-mail generated by using the mailer to the terminal 5A, the terminal 5B performs switching between transmission through a mobile phone communication network and transmission directly to the terminal 5A by use of the near-field wireless communication (near mode).

Hereinafter, processing for data transfer in the near mode performed between the mobile phone terminals 5A and 5B will be described in detail. FIG. 21 is a sequence diagram showing the processing for data transfer performed between the terminals 5A and 5B. Note that in FIG. 21, the terminal 5A serves as the reception side upon data transfer in the near mode, and the terminal 5B serves as the transmission side.

At Steps S901 and S902, the terminals 5A and 5B initiate the operation of the respective near-field wireless communication circuits 10. At Steps S903 and S904, the terminals 5A and 5B mutually detect the opposite terminal.

At Step S101 shown in FIG. 21, the terminals 5A and 5B connect in the normal mode to each other by using the respective near-field wireless communication circuits 10, based on the control by the respective controllers 13 included therein. At Step S905, the terminals 4A and 4B perform, in the normal mode, preliminary processing on data transfer in the near mode (Step S107) which will be performed later.

FIG. 22 is a sequence diagram showing a specific example of the preliminary processing performed at Step S905. At Step S1001, the terminal 5B displays on the display unit 14 detection of the authenticated terminal 5A. Note that in a case where the terminal 5A has not been approved, authentication processing for the terminal 5A may be executed. The procedure of the authentication mentioned in the forth exemplary embodiment of the invention may be used for this authentication processing. Further, when the terminal 5B authenticates the terminal 5A, it may store a phone number and an e-mail address allocated to the terminal 5A, and information for identifying the terminal 5A such as a name or a nickname of the user in association with the connection key exchanged upon the authentication. Thus, when the authenticated terminal 5A is detected, it is possible to notify the user of the terminal 5A being the authenticated one and of the information on the user (phone number, e-mail address) by outputting them to the display unit 14.

At Step S1002, the terminal 5B activates the mailer in response to the operation by the user. At Step S1003, the terminal 5B accepts, through the operation accepting unit 15, operation for designating a destination e-mail address and a data file attached to a mail to be transmitted.

At Step S1004, the terminal 5B determines a path for transmitting the e-mail in response to operation by the user for instructing transmission. Mentioned in more detail, the terminal 5B determines to transmit the e-mail through the mobile phone communication network (cellular network), if the size of transmitted data is equal to or smaller than a predetermined data size. Note that if the size of transmitted data is equal to or smaller than the predetermined data size, it may be determined whether or not the destination of the e-mail is a terminal which can conduct the near-field wireless communication. If the destination of the e-mail is the terminal which can conduct the near-field wireless communication, it may be determined to transmit the e-mail in the normal mode (Step S1005).

On the other hand, if the size of transmitted data exceeds the predetermined data size and the destination of the e-mail is the terminal which can conduct the near-field wireless communication, the terminal 5B determines to transmit the e-mail in the near mode. In this case, the terminal 5B transmits an instruction for reception in the near mode to the terminal 5A (Step S1006). Operation at Steps S304 and S305 in FIG. 22 is similar to that mentioned hereinbefore.

As mentioned above, the wireless communication system according to this exemplary embodiment selects, depending on the size of transmitted data, a path for data transmission from among a plurality of candidates (mobile phone communication network, near-field wireless (normal mode), and near-field wireless (near mode)). Therefore, it is possible to select an appropriate path for the data transmission according to the amount of transmitted data.

Sixth Exemplary Embodiment of the Invention

FIG. 23 shows configuration of a wireless communication system according to this exemplary embodiment. The wireless communication system according to this exemplary embodiment includes a mobile phone terminal 6A and a kiosk terminal 6B which can conduct near-field wireless communication. Furthermore, the wireless communication system according to this exemplary embodiment includes a mobile phone communication network and a server 84. FIG. 23 shows a base station 80 and a core network 82 which is connected to the base station 80, as an example of elements included in the mobile phone communication network.

The mobile phone terminal 6A and the kiosk terminal 6B are located in a cell 81 formed by the base station 80. The server 84 is connected to the core network 82 through the Internet 83. The server 84 can be accessed from the mobile phone terminal 6A through the mobile phone communication network. Further, the server 84 can communicate with the kiosk terminal 6B for the purpose of delivering content data. In order to suit the delivery of the content data, the kiosk terminal 6B and the server 84 may be connected by a higher-speed line as compared with a radio channel between the base station 80 and the mobile phone terminal 6A. For example, the kiosk terminal 6B may connect to the Internet 83 by using an ADSL (Asymmetric Digital Subscriber Line) or an optical fiber line, each of which is provided by a carrier.

Note that the arrangement of the server 84 shown in FIG. 23 is no more than an example. The server 84 has only to be capable of being accessed from the mobile phone terminal 6A through the mobile phone communication network, and of communicating with the kiosk terminal 6B. For example, the server 84 may be arranged as equipment of a mobile phone carrier in the mobile phone communication network. Further, the server 84 may be a collection of plural computers. For example, a computer which accepts access from the mobile phone terminal 6A, a computer which delivers the content, and a computer which performs the payment processing may be the individual ones.

Hereinafter, there will be described transfer processing for the content data in the near mode, which is executed between the mobile phone terminal 6A and the kiosk terminal 6B. FIG. 24 is a sequence diagram showing processing for data transfer executed between the terminals 6A and 6B. Note that in FIG. 24, the terminal 6A serves as the reception side upon data transfer in the near mode, and the terminal 6B serves as the transmission side.

At Step S1101, the mobile phone terminal 6A accesses the server 84 through the mobile phone communication network. At Step S1102, the mobile phone terminal 6A accepts, through the operation accepting unit 15, operation for selecting content to be downloaded from the server 84. At Step S1103, the terminal 6A checks a file size of the content selected as the object of download. When the file size is smaller than a predetermined value (X bytes), the mobile phone terminal 6A determines to download the content through the mobile phone communication network (Step S1104).

On the other hand, when the file size is equal to or larger than the predetermined value (X bytes), the mobile phone terminal 6A determines to download the content by using the near-field wireless communication in the near mode with the kiosk terminal 6B. In this case, the mobile phone terminal 6A initiates the operation of the near-field wireless communication circuit 10 (Step S1105).

At Steps S1106 and S1107, the mobile phone terminal 6A and the kiosk terminal 6B mutually detect the opposite terminal. At Step S1108, the mobile phone terminal 6A outputs information on a group of terminals detected at Step S1106 to the display unit 14. Then, the mobile phone terminal 6A accepts, by the operation accepting unit 15, operation for selecting a terminal to be wirelessly connected from among the detected group of terminals. At Step S101 in FIG. 24, the mobile phone terminal 6A connects in the normal mode to the selected terminal (kiosk terminal 6B).

At Step S1109, the mobile phone terminal 6A and the kiosk terminal 6B perform, in the normal mode, preliminary processing on data transfer in the near mode (Step S107) which will be executed later. FIG. 25 is a sequence diagram showing a specific example of the preliminary processing performed at Step S1107. At Step S1201 in FIG. 25, the mobile phone terminal 6A transmits information on the content selected as the object of download to the kiosk terminal 6B. At Step S304 in FIG. 25, the kiosk terminal 6B transmits to the mobile phone terminal 6A an instruction to start the determination of the availability of the near mode. At Step S305, the mobile phone terminal 6A outputs the message for prompting the touch to the display unit 14. The message may be displayed on the kiosk terminal 6B.

At Step S1202, the kiosk terminal 6B initiates preliminary acquisition of the content designated as the object of download from the server 84. That is, the kiosk terminal 6B initiates the acquisition of the content from the server 84 based on the content information obtained in the process of the preliminary processing, in advance of initiation of transmitting the content in the near mode at the subsequent Step S107. Note that the process at S1202 may be performed before Step S304 or in parallel with the process at S304.

Returning to FIG. 24, the description is continued. Operation of the terminals 6A and 6B at Steps S103 to S106 in FIG. 24 may be similar to that of the terminals 1A and 1B at the corresponding Steps described in FIG. 5. At Step S107 in FIG. 24, the content is transmitted in the near mode from the kiosk terminal 6B to the mobile phone terminal 6A.

Finally, at Step S1110, the mobile phone terminal 6A acquires an encryption key (reproduction key) required for using (e.g., reproducing and viewing) the content through the mobile phone communication network. Note that the server 84 may perform processing for charging and authenticating the user, and thus may transmit the reproduction key only when it is determined that the user of the mobile phone terminal 6A has the authority to use the content. The server 84 may corporate with an accounting server of the mobile phone carrier, so that the charge of the content can be sent together with mobile phone charges. Further, the mobile phone terminal 6A may acquire the reproduction key from the kiosk terminal 6B. Further, the mobile phone terminal 6A may acquire a connection key from a mobile telephone line.

By use of the wireless communication system according to this exemplary embodiment, the mobile phone carrier can avoid an increase in traffic flowing across the mobile phone communication network. The mobile phone carrier can also earn sales of the content in addition to the charge of the mobile phone terminal 6A, by comprehensively operating the server 84 and the kiosk terminal 6B. Further, the mobile phone terminal 6A can acquire the content at high speed in a short time through the kiosk terminal 6B. Therefore, it is possible to reduce electric power required for acquiring the content.

Note that in the above description of this exemplary embodiment, there have been described the case where the content is downloaded from the server 84 to the mobile phone terminal 6A. Meanwhile, this exemplary embodiment can be also applied to an upload of large-volume data from the mobile phone terminal 6A to the server 84. For the upload to the server 84, the direction of the data transfer at Steps S1104 and S107 may be reversed.

By the way, the control of the processing for the data transfer which is executed mainly by the controller 13 described, in each of the first to sixth exemplary embodiments of the invention, in other words, the control of the terminals for executing the data transfer in the near mode after performing the preliminary processing in the normal mode can be materialized by causing a computer such as a microprocessor to execute a control program. Specifically, the processes in each terminal shown in FIGS. 5, 6, 7, 13, 16 to 19, 21, 22, 24 and 25 may be executed by the computer. The control program can be stored in various types of storage media, and can be transmitted through communication media. Examples of the storage media include a flexible disk, a hard disk, a magnetic disk, a magnet-optical disk, a CD-ROM, a DVD, a ROM cartridge, a RAM memory cartridge with battery backup, a flash memory cartridge, and a nonvolatile RAM cartridge. Further, the communication media include a wired communication medium such as a telephone line, a wireless communication medium such as a microwave line, and the Internet.

Further, in the above-mentioned first to sixth exemplary embodiments, the mobile phone terminal, the kiosk terminal, and the portable music and video player are shown as specific examples of the wireless communication terminal. Meanwhile, it is obvious that the wireless communication terminal, which performs the preliminary processing in the normal mode and performs the data transfer in the near mode, is not limited to the above-described specific examples. For example, the wireless communication terminal described in each exemplary embodiment may be a computer device such as a PC (personal computer) or a PDA, or may be a data recording device such as an HD (Hard Disc) recorder.

In the first to sixth exemplary embodiments of the present invention described above, the specific example in which the communication method in the near mode of the near-field wireless communication circuit 10 is the DS-SS method is described. However, the communication method in the near mode may be a combination of the DS-SS method with time-frequency hopping as already described. Further, the communication method in the near mode may be a hybrid method combining the DS-SS method and a FH-SS (Frequency Hopping Spread Spectrum) method.

Although the present invention is described in reference to the exemplary embodiments in the foregoing, the present invention is not limited thereto. Various changes and modifications as would be obvious to one skilled in the art may be made to the structures and details of the present invention within the scope of the present invention.

This application is based upon and claims the benefit of priority from Japanese patent application No. 2008-298936, filed on Nov. 25, 2008, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   1A, 1B, 2A, 2B, 4A, 4B TERMINAL -   3A, 5A, 5B, 6A MOBILE PHONE TERMINAL -   3B, 6B KIOSK TERMINAL -   10 NEAR-FIELD WIRELESS COMMUNICATION CIRCUIT -   11 ANTENNA -   12 MEMORY -   13 CONTROLLER -   14 DISPLAY UNIT -   15 OPERATION ACCEPTING UNIT -   100 ANALOG FRONT END (AFE) -   101 A/D CONVERTER (ADC) -   102 FFT UNIT -   103 DE-MODULATOR -   104 DECODER -   105 MAC UNIT -   106 CODER -   107 MODULATOR -   108 IFFT UNIT -   109 D/A CONVERTER (DAC) -   30 Mobile Phone Communication Circuit -   31 ANTENNA -   40 TRANSMISSION FRAME -   41 PREAMBLE AND HEADER -   42 PAYLOAD -   71, 72 BEACON SIGNAL -   73 PREAMBLE -   74 HEADER -   75 PAYLOAD -   76 TEST SIGNAL -   77 TRANSMISSION DATA SIGNAL -   80 BASE STATION -   81 CELL -   82 CORE NETWORK -   83 INTERNET -   84 SERVER -   2601 LOW NOISE AMPLIFIER -   2602 QUADRATURE MIXER -   2603 LOCAL SIGNAL GENERATOR -   2604 COMPLEX FILTER -   2605 LOW PASS FILTER -   2606 VARIABLE GAIN AMPLIFIER -   2701 INPUT SIGNAL TERMINAL -   2702 HIGHER REFERENCE VOLTAGE -   2703 LOWER REFERENCE VOLTAGE -   2704 LADDER RESISTOR -   2705 COMPARATOR UNIT -   2706 RESOLUTION SWITCHING TERMINAL 

1. A wireless communication device comprising: a near field wireless communication circuit being capable of switching between a first communication mode to perform OFDM (Orthogonal Frequency Division Multiplexing) and a second communication mode with a relatively short communicable distance as compared with that in the first communication mode and to perform spread spectrum; and a control unit being capable of controlling the switching between the first and second communication modes, wherein the control unit is adapted to: execute, with a destination device through the near field wireless communication circuit that is set to the first communication mode, preliminary processing needed for initiating data transfer in the second communication mode with the destination device; determine availability of the data transfer in the second communication mode with the destination device by using a measured value of communication quality related to a communication distance to the destination device as a measure of the determination; and initiate, when it is determined that the data transfer is available, the data transfer by using the near field wireless communication circuit that is set to the second communication mode, based on a result of the preliminary processing.
 2. The wireless communication device according to claim 1, wherein in the determination of the availability of the data transfer, the control unit starts measurement of communication quality in the first communication mode, makes transition to measurement of communication quality in the second communication mode in response to satisfaction of predetermined criteria by the communication quality in the first communication mode, and determines that the data transfer are available when the communication quality in the second communication mode satisfies predetermined criteria.
 3. The wireless communication device according to claim 1, wherein in the determination of the availability of the data transfer, the control unit operates the near field wireless communication circuit so as to perform the switching between the first communication mode and the second communication mode in a time-division manner, and performs the measurement of the communication quality in the second communication mode, while retaining synchronization with the destination device by communicating a beacon signal in the first communication mode.
 4. The wireless communication device according to claim 3, wherein the beacon signal includes designation of a transmission period of a wireless signal from the destination device in the second communication mode, and the control unit performs the measurement of the communication quality in the second communication mode during the transmission period designated by the beacon signal.
 5. The wireless communication device according to claim 3, wherein upon performing the data transfer, the control unit operates the near field wireless communication circuit to transmit the beacon signal in the first communication mode, and transmit or receive target data of the data transfer in the second communication mode.
 6. The wireless communication device according to claim 3, wherein upon performing the data transfer, the control unit switches the communication mode for communicating the beacon signal from the first communication mode to the second communication mode.
 7. The wireless communication device according to claim 1, wherein the control unit performs a search of a device that can communicate in the second communication mode by using the wireless communication circuit that is set to the first communication mode.
 8. The wireless communication device according to claim 7, further comprising: a far field wireless communication circuit being capable of wirelessly connecting to a base station included in a mobile phone communication network; and a determination unit being capable of conducting data communication through the far field wireless communication circuit with a server that can be accessed through the mobile phone communication network, and for determining, according to a data size of content to be downloaded from the server, through which of wireless connection to the mobile phone communication network and near field wireless connection to the communication destination device to download the content, wherein the control unit performs the search of the device that can communicate in the second communication mode, in response to the determination of the download through the near field wireless connection.
 9. The wireless communication device according to claim 7, further comprising: a display unit; and an operation accepting unit being capable of accepting input operation by a user, wherein the control unit outputs information on at least one device detected by the search to the display unit, and accepts an instruction designating the destination device from among the at least one device through the operation accepting unit.
 10. The wireless communication device according to claim 1, further comprising: a second communication circuit that is different from the near field wireless communication circuit, wherein the control unit initiates preliminary acquisition of target content of the data transfer from a server that can be accessed through the second communication circuit, in response to execution of the preliminary processing in the first communication mode or execution of the determination of the availability of the data transfer.
 11. The wireless communication device according to claim 1, further comprising a closeness degree display unit being capable of displaying a degree of closeness of the wireless communication device and the destination device, wherein the control unit changes a state of the display by the closeness degree display unit so as to indicate that the degree of closeness rises according to rising of the communication quality.
 12. The wireless communication device according to claim 1, wherein the preliminary processing includes at least one of displaying a message to a user of the wireless communication device and accepting input operation by the user.
 13. The wireless communication device according to claim 12, wherein the preliminary processing includes at least one of: (a) checking vacancy in a memory for reception of the destination device and displaying a result of the check to the user; (b) securing, performed with the input operation by the user, a free space at the memory for reception by removing data from the memory for reception; (c) designating, performed with the input operation by the user, target content of the data transfer; (d) making electronic payment performed with the input operation by the user; and (e) authenticating the destination device performed with the input operation by the user.
 14. The wireless communication device according to claim 1, wherein the control unit performs, with the destination device in the second communication mode in advance of the initiation of the data transfer, exchange of a connection key for encrypting data to be transferred in the data transfer.
 15. The wireless communication device according to claim 1, wherein the communication quality includes at least one of an RSSI (Received Signal Strength Indicator), an LQI (Link Quality Indicator), and a bit error rate.
 16. The wireless communication device according to claim 1, wherein the first communication mode is a communication mode with an average transmitted power of equal to or lower than −41.3 dBm/MHz and using at least a first bandwidth of about 500 MHz included in a range from 3.1 GHz to 10.6 GHz, and the second communication mode is a communication mode with an average transmitted power of equal to or lower than −70 dBm/MHz and using an A/D converter with a lower resolution as compared with that in the first communication mode.
 17. A wireless communication system comprising first and second communication devices, wherein each of the first and second communication devices includes a near field wireless communication circuit being capable of performing switching between a first communication mode to perform OFDM and a second communication mode with a relatively short communicable distance as compared with that in the first communication mode and to perform spread spectrum, wherein the first and second communication devices execute, through the respective near field wireless communication circuits that are set to the first communication mode, preliminary processing needed for initiating data transfer in the second communication mode between the first and second communication devices, wherein the first communication device determines availability of the data transfer in the second communication mode with the second communication device by using a measured value of communication quality related to a communication distance as a measure of the determination, wherein when it is determined that the data transfer is available, the first and second communication devices initiate the data transfer by using the respective near field wireless communication circuits that are set to the second communication mode, based on a result of the preliminary processing.
 18. The wireless communication system according to claim 17, further comprising: a server that can be accessed from one of the first and second communication devices through a mobile phone communication network, wherein said one communication device further comprises: a far field wireless communication circuit being capable of wirelessly connecting to a base station included in the mobile phone communication network; and a determination unit being capable of conducting data communication with the server through the far field wireless communication circuit, and for determining, according to a data size of content to be downloaded from the server, through which of wireless connection to the mobile phone communication network and near field wireless connection to the communication destination device to download the content.
 19. The wireless communication system according to claim 18, wherein another of the first and second communication devices further comprises a second communication circuit that can communicate with the server not through the base station, wherein said another communication device initiates preliminary acquisition of target content of the data transfer from the server through the second communication circuit, in response to execution of the preliminary processing in the first communication mode or execution of the determination of the availability of the data transfer.
 20. A method of controlling a wireless communication device, the device including a near field wireless communication circuit, the method comprising: executing, with a destination device through the near field wireless communication circuit that is set to a first communication mode, preliminary processing needed for initiating data transfer in a second communication mode with the destination device, the first communication mode being a communication mode to perform OFDM and the second communication mode being a communication mode with a relatively short communicable distance as compared with that in the first communication mode and to perform spread spectrum; determining availability of the data transfer in the second communication mode with the destination device by using a measured value of communication quality related to a communication distance to the destination device as a measure of the determination; and initiating, when it is determined that the data transfer is available, the data transfer by using the near field wireless communication circuit that is set to the second communication mode, based on a result of the preliminary processing.
 21. A recording medium storing a program, the program causing a computer to execute control processing for a wireless communication device, the device including a near field wireless communication circuit, the control processing comprising: executing, with a destination device through the near field wireless communication circuit that is set to a first communication mode, preliminary processing needed for initiating data transfer in a second communication mode with the destination device, the first communication mode being a communication mode to perform OFDM and the second communication mode being a communication mode with a relatively short communicable distance as compared with that in the first communication mode and to perform spread spectrum; determining availability of the data transfer in the second communication mode with the destination device by using a measured value of communication quality related to a communication distance to the destination device as a measure of the determination; and causing, when it is determined that the data transfer is available, the near field wireless communication circuit that is set to the second communication mode to initiate the data transfer, based on a result of the preliminary processing. 